1. Field of the Invention
This invention relates to a circulating valve for use in a well. Circulating valves are used to permit flow between two well conduits.
2. The Prior Art
In the completion or production of a well, a circulating valve is often installed to permit a high volume rate of flow between two of the well conduits. For example, it may be desired to kill a producing well to perform any one of several operations. A circulating valve controlling flow between the tubing string bore and the annulus around the tubing string would be opened. Fluid would then be circulated through the circulating valve to kill the well.
Generally, circulating valves have been actuated by the use of wireline tools extending from the surface down into the well. For a deep well, the use of wireline tools is expensive, poses a hazard of possible loss of tools in the well, requires time to run the tools into the well, and requires manipulation from the surface to affect opening of the valve.
Some circulating valves are pressure operated. U.S. Pat. No. 3,282,348 to Artigue discloses a pressure operated circulating valve which permits uni-directional flow through the valve and which moves to a closed position preventing any flow through the valve upon the application of a predetermined pressure differential across the valve. U.S. Pat. No. 3,807,428 to Watkins, et al discloses a circulating valve which is opened upon the application of a predetermined first absolute pressure, and which is closed upon the application of a predetermined second higher absolute pressure.
Neither of the circulating valves disclosed in the above patents permits any condition of flow through the valve once the valve is opened. In addition, the circulating valve disclosed in Watkins et al '428 would be uncontrollable in the event that tubing pressure could not be controlled from the surface.